This one will be short and sweet, I have been playing this game for a while and there has been one issue that I have had since the alpha. Spells with a given duration are hard to track in terms of when they expire.
Second part of this post is my simple suggestion for a fix. Either under the row that shows your minions or on the bottom left bar where buffs are shown, show the cast spells and the duration they have left. For example, when I cast a self channeled Avalanche, show the skill icon with the exact same clock-like design as buffs and debufs. You can even go the extra mile and show number of seconds left inside the skill icon.
A similar thing would be great for temporary companions, such as thorn totems for example. being able to see how close they are to expiring would help gameplay and build fluidity quite a bit.